1) If you use multiple compression drivers you can play 'em lower... Note that Danley used to use expensive coaxial compression drivers in some of the Synergy and Genesis horns, and he's mostly abandoned that. If I had to hazard a guess, I'd say that it's likely easier and more cost effective to use 2-4 compression drivers than it is to use a single coaxial compression driver. The main limitation keeping you from using a compression driver below 1000hz is excursion, so the use of multiple compression drivers on a Paraline is attractive because they sum very nicely at low frequencies.

Basically, investing $300 in a pair of compression drivers might be less hassle and less maddening than trying to get the midranges to go to 2000hz. Or you might consider some of the less expensive options from Celestion, thought that might open another can of worms. (I can't recall if the Celestion has as much displacement as the BMS. If it doesn't, then stick with the BMS, because displacement rules the day when it comes to setting the xover low.)

2) IMHO, if you're going to use a single frustum, you should have it centered in front of the cone of the midrange. This equalizes the pathlengths. A frustum is basically a crude phase plug, so centering it is important.

When I did the ports as they are, I wasn't worried about getting it centered because I figured that the path lengths from the cone itself in the chamber to the port would be short enough that any effect would be outside the bandpass. Thinking about it I'm probably right on the edge.

Another thing I didn't consider (as you guys mentioned) along those lines is the furthest part of the cone from the center of the comp driver entrance is nearly 2.5" farther away than the near side of the cone. Interesting to think about, and that could also be limiting my bandwidth, even though it seems on the surface counter-intuitive to move the ports farther out. I'll try moving the ports this weekend.

Nissep - that's more than I want to wrap my brain around at this hour but you're probably right. I only went 4th order because that's what fell out from the way the mid ports are configured and that's where the comp driver falls off. I added 1st order electrical high and low-pass to the drivers to hit about 4th order acoustic and to protect the drivers. Mainly, I just wanted a quick impression of how these things are going to sound!

Actually I won't, at least not with 4 drivers. The ports are already close to the Paraline fold as it is. I did cut some extra driver plates in anticipation of trial and (lots of!) error, so I might try out 2 drivers with centralized ports and frustrums.

That's one of the nice things about these Paralines. I can fairly easily redo the driver configuration on a flat plate without having to cut up the horn shell.

I'm also going to look into reticulated foam or poly fill in the frustrums as well as the Paraline itself to smooth the response.

There has been some talk about using the Paraline as a bass-/midbasshorn. If you design a tall Paraline, you should be able to reach down to bass/midbass territory. I have spent some time visualizing this and thinking about how nice it would be to shorten the depth of a proper 60-300 horn with a combination of a tall Paraline and a relatively short horn in front.

I have tried to model the Paraline in Hornresp. With only one driver and designing for midbass duties, I have tried different sizes for S1, S2 and L12. There is not much horn-gain in the lower frequencies with a Paraline designed with 1 inch height in the "layers", even modelling a 200cm version.

Of course, I may be doing this all wrong. How would one go about modelling a Paraline in Hornresp? Naively, I used S1 for entry, S2 for exit/the "slot" and L12 for pathlength=A1 in the patent. Have I missed something?

I tried searching for Paraline and Hornresp but could not find any info.

Using 2" thickness/heigth in the layers of the Paraline improved matters quite a lot in my (most probably wrong) Hornresp model.

A 120cm tall Paraline combined with a conical horn of 60cm with (120cm height) and 52cm length gives me F3 70Hz and 106dB sensivity. As the total pathlength is around 112 cm there should be some gain even at frequencies under 100Hz? I set the backchamber at 15 liters, have not played around much with the other parameters.

I used a JBL 2226 for modelling, even if this driver is not optimal for horns. Having seen quite experienced people using it in La Scala and Altec horns, I am hoping to find use for my stock of this driver.

Naturlyd,
I suspect that what you are seeing is the fact that the Paraline and conic horn combination is more of a directional device than a gain device. You only have to go and look at some of the original horn development to see that a conic section is not an efficient shape as far as gain is concerned. It has been chosen in the original design concept to control directivity in large arrays. What you have given up in efficiency is made up by more amplifier power and lots of eq.

When you are looking at the output of the Paraline you need to look at the complete Paraline and horn combination, not just to the initial section only. S2 should be the final horn mouth size not the end of the Paraline.

Naturlyd,
I suspect that what you are seeing is the fact that the Paraline and conic horn combination is more of a directional device than a gain device. You only have to go and look at some of the original horn development to see that a conic section is not an efficient shape as far as gain is concerned. It has been chosen in the original design concept to control directivity in large arrays. What you have given up in efficiency is made up by more amplifier power and lots of eq.

When you are looking at the output of the Paraline you need to look at the complete Paraline and horn combination, not just to the initial section only. S2 should be the final horn mouth size not the end of the Paraline.

Thank you very much, Kindhornman, I did not realise that Conicals is so much less efficient regarding gain, but do remember that TD wrote about the upside of controlled directivity. For midbass I think gain is my main priority.

I did model the horn in two sections, first the Paraline S1-S2 and then a conical section S2-S3. The Paraline do have a rather narrow expansion with S1 set to 340cm2 (2:1 in compression with JBL 2226) and S2 set to 528cm2 (a 120cm tall and 4.4cm wide slot/exit). Using a conical section after the Paraline, the results from using a wider expansion looks much better to this untrained eye, with more lowfrequency gain and smoother graphs.

Things I need to learn:

- will a "slimmer" Paraline with D1 less than A1 and a diverging wavefront "load" the following horn better as it "uses" the vertical part of the following horn to a greater extent?

- As the Paraline output is rather extreme, having a more or less flat wavefront in the vertical and 360 in the horisontal, how will this affect the next section of the horn when optimizing for midbass/bass purposes?

- Do I have to use a conical section after the Paraline to get the optimal interface? Why not a exponential horn?

- Do the shading-effect on the Paraline affect the interface with a following horn-section?

I tried searching for Paraline and Hornresp but could not find any info.

Using 2" thickness/heigth in the layers of the Paraline improved matters quite a lot in my (most probably wrong) Hornresp model.

A 120cm tall Paraline combined with a conical horn of 60cm with (120cm height) and 52cm length gives me F3 70Hz and 106dB sensivity. As the total pathlength is around 112 cm there should be some gain even at frequencies under 100Hz? I set the backchamber at 15 liters, have not played around much with the other parameters.

I used a JBL 2226 for modelling, even if this driver is not optimal for horns. Having seen quite experienced people using it in La Scala and Altec horns, I am hoping to find use for my stock of this driver.

But am I modelling this as it should be done?

I need a break from writing code at work, so thought I'd throw together some quick instructions on basshorn paralines.

here is how I would do it.

1) First off, we need to set a goal for the project. I'm going to 'aim' for an F3 of about 30hz. My selection of 30hz is a compromise between home theater and music. (IMHO home theater needs to go to about 20hz, music needs a sub that does 35hz or so.)

Here is the math on what size Paraline we need.
The Paraline cutoff will be equivalent to the distance from the center of the Paraline to the 'top' of the Paraline, divided by four. For instance, with a 366cm x 732cm board, the distance from center to top is 366cm. The formula is (speed of sound / distance / 4), or (34000 cm per second / 366cm / 4), or 23hz.

2) Now that we know how low our Paraline will play, we have to pick a driver for the project. I'm going with a back loaded horn using the ubiquitous MCM 55-2421. I'm selecting this driver for two reasons. First, it's twenty five bucks. Second, it's a very "horn-friendly" driver, due to it's low qes.

In order to ease the use of hornresp with Paralines, I made a spreadsheet. The pic above shows the spreadsheet.

Using the spreadsheet is really simple, you simply plug in the longest dimensions of your paraline, and the internal thickness.

Once you plug in those two numbers, the spreadsheet will give you the following data:

1) it'll tell you the quarter wavelength frequency of your horn. For a BLH I'd aim for 0.707 multiplied by the FS of the driver. For instance, a driver with an FS of 30.95hz would have an FB of 22hz.
2) it'll tell you the area of the segments in hornresp. For instance, it'll tell you what to plug in for entries "S2,S3,S4 and S5" in hornresp
3) it'll tell you the maximum usable frequency of the Paraline
4) it'll tell you the internal volume of a Paraline

you can get the spreadsheet here:https://docs.google.com/spreadsheet/...oWEVYRmc#gid=0
You may need to cut and paste the formula into excel, or your own google spreadsheet. I set up the spreadsheet so that you can see it, but you can't change it. I did this so that no one messes with the formulas.